.. _wcslib: http://www.atnf.csiro.au/people/mcalabre/WCS/wcslib/index.html
.. _distortion paper: http://www.atnf.csiro.au/people/mcalabre/WCS/dcs_20040422.pdf
.. _SIP: http://irsa.ipac.caltech.edu/data/SPITZER/docs/files/spitzer/shupeADASS.pdf
.. _ds9: http://ds9.si.edu/
.. _FITS WCS standard: https://fits.gsfc.nasa.gov/fits_wcs.html
